This invention relates to a digital electronic still-video camera for picking up the image of a subject and recording image data representing the image of the subject on a recording medium, and to a method of controlling the operation of this camera.
In a digital electronic still-video camera, image data obtained by picking up the image of a subject is stored temporarily in an internal image memory, the image data is read out of the image memory and is then subjected to various signal processing such as processing for generating a luminance signal, processing for generating color difference signals and processing for compression and decompression of data.
A plurality of image memories having prescribed storage capacities are connected in parallel with a circuit that executes various signal processing. If the image data becomes large in quantity, the number of image memories also increases. If a large number of image memories are used, the address lines and data lines connected to these memories also become large in number and the amount of power necessary to drive the address and data lines increases as well.
If the amount of image data increases, moreover, so does the amount of signal processing. In order to shorten the time required for various signal processing, it is necessary to raise the speed at which data is accessed. However, increasing the data access speed increases the amount of power consumption as well.
Accordingly, an object of the present invention is to provide a digital electronic still-video camera and a method of controlling the operation thereof in which it is possible to reduce the amount of power consumption.
According to the present invention, the foregoing object is attained by providing a digital electronic still-video camera for obtaining image data representing the image of a subject by picking up the image of the subject using image sensing means, and recording the obtained image data on a recording medium, comprising: a plurality of memory modules each of which includes an image memory to and from which image data can be written and read, and an image memory control circuit responsive to an applied standby/active control signal for placing the image memory in a standby or active state and controlling the image memory in such a manner that when the image memory has been placed in the active state, image data obtained from the image sensing means is written to the image memory or image data that has been written to the image memory is read out of the image memory; and a memory module control circuit for applying the standby/active control signal to the image memory control circuits included in the plurality of memory modules.
The present invention further provides an operation control method suited to the camera described above. Specifically, the present invention provides a method of controlling operation of a digital electronic still-video camera for obtaining image data representing the image of a subject by picking up the image of the subject using image sensing means, and recording the obtained image data on a recording medium, comprising the steps of: providing a plurality of memory modules each of which includes an image memory to and from which image data can be written and read, and an image memory control circuit responsive to an applied standby/active control signal for placing the image memory in a standby or active state and controlling the image memory in such a manner that when the image memory has been placed in the active state, image data obtained from the image sensing means is written to the image memory or image data that has been written to the image memory is read out of the image memory; and applying the standby/active control signal to the image memory control circuits included in the plurality of memory modules.
In accordance with the present invention, the standby/active control signal is output by the memory module control circuit and applied to the image memory control circuit. The image memory is controlled so as be placed in the standby or active state in dependence upon the standby/active control signal that has entered the image memory control circuit.
When the image memory has been placed in the active state, image data obtained by image pick-up is written to the memory or image data that has been written to the memory is read out.
In accordance with the present invention, the image memories included in the plurality of memory modules can be controlled so as to be placed in the standby or active state. Since image memories not necessarily required for various signal processing can be placed in the standby state, power consumption can be reduced.
By way of example, the memory module control circuit applies the standby/active control signal to the image memory control circuit in such a manner that when the image memory included in one memory module among the plurality of memory modules is in the active state, the image memory included in at least one memory module among the other memory modules is placed in the standby state.
The plurality of memory modules may be freely attachable to and detachable from the image sensing means.
When the image sensing means and the image memories included in the plurality of memory modules are connected via a common bus, the image memory control circuits included in the plurality of memory modules each output a signal indicative of a bus-use request to the memory module control circuit. The memory module control circuit includes decision means (a decision device) for deciding, on the basis of the bus-use request signals input thereto, the image memory control circuit that is allowed to use the bus, and enabling signal output means (an enabling signal output device) for outputting a bus-use enabling signal to the image memory control circuit allowed to use the bus by the decision means.
Since the memory control circuit allowed to use the bus is capable using the bus, data collision can prevented even though the bus is a common bus.
Preferably, the memory module control circuit selects an image memory, to which image data obtained by the image sensing means is written, in dependence upon the storage capacities of the image memories included in the plurality of memory modules.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.